uplander Instrument Cluster bulbs

recently bought a 2005 uplander with 72,000 miles. had 1 bulb not working in the instrument cluster. took the cluster assembly out ot inspect and took a bulb from another section and replace to see if it was the bulb or the curcuit board. the second bulb did not work either. When I replace the second bulb in it's original spot, it would not work. now I have two bulbs out and still no understanding of why. only thing I can see is a slight scratch in the green coating in the circuit board where the bulbs twisted in and out. would the absence of this green material cause a bulb to not make contact, or is there something else going on here?